Blood cells are the primary guardians against diseased states, both as a result of pathogens and cellular aberration. Cells of both the lymphoid and myeloid lineages are involved with the monitoring of the health of the host. Because of the diversity of situations involved with protecting the host, a variety of mechanisms have evolved. While some of the mechanisms are selective, other mechanisms are non-selective in their mode of attack. Thus, not only can the disease associated component be attacked, but also native tissue. Particularly, neutrophils employ a variety of mechanisms for cytotoxicity which are non-selective. In many situations, it would be of interest to know whether neutrophils have become activated to determine whether the body is responding to a particular event, either constructively or destructively.